DOMAIN POPULATIONS IN EPITAXIAL FERROELECTRIC THIN-FILMS - THEORETICAL CALCULATIONS AND COMPARISON WITH EXPERIMENT

An equilibrium domain theory is used to calculate the thickness and te mperature dependencies of relative domain populations in tetragonal fe rroelectric thin films epitaxially grown on cubic substrates. The rela tive coherency strain between the film and substrate that governs doma in configurations is evaluated with the account of strain accomodation caused by the generation of misfit dislocations at the growth tempera ture. The threshold coherency strain, which provides the energetic equ ivalency of the c and a single-domain films and plays an important rol e in predicting multidomain patterns, is computed as a function of tem perature with the aid of the Landau-Ginsburg-Devonshire-type thermodyn amic theory. Theoretical predictions are compared with the experimenta l measurements for PbTiO3 films grown on (001)-oriented MgO and KTaO3 substrates and found to be in good agreement in both the thickness and temperature dependence of the c-domain volume fraction in these epita xial heterostructures. (C) 1996 American Institute of Physics.